Reticulate metal structures have been generated heretofore for many purposes. For example, such structures may provide a conductive network suitable for use as supports in batteries in which an active material is applied to and held in place by the supports or is formed on the support.
Depending upon the porosity of the structures, they may be used as sieves, screens or the like.
Porous and reticulate metal structures and structures of other materials such as alloys, semiconductors or ceramics, moreover, may be used as active materials as battery electrodes, or as catalytic materials or catalyst supports because of the relatively high surface area to volume ratio which the reticulate structures manifest.
In the past, the structures have been formed by chemical vapor deposition, electroless deposition and even electroplating techniques on a fibrous support, e.g. a nonwoven fabric or needled fabric of synthetic resin fibers, which can be pyrolyzed to eliminate the fiber and leave a reticulate metal structure.
When electroplating techniques are used, it is necessary to pretreat the support so as to make it sufficiently conductive to allow the electroplating process to operate Whether the metal material is applied to the support by electroplating or other prior art deposition techniques which have been used for this purpose, the deposit which is formed tends to be highly regular, i.e. with a minimum of sharp-edged angled surfaces on a microscopic level. Thus, while the prior art reticulate metal structures have a comparatively large surface area to volume ratio, that ratio is nevertheless limited by the method which has been used in the production of the product.
I have now discovered that, when low temperature arc vapor deposition is used to deposit a material adapted to form a porous structure on an openwork support, the product so made is subjected to pyrolysis, and the structure which remains after pyrolysis is sintered into a coherent body, the resulting product is characterized inter alia by a surprisingly larger surface area to volume ratio than can be obtained by electrodeposition techniques and other systems heretofore used in the formation of such reticulate structures.
The techniques which I have developed as described in the aforementioned application and patents appear to be ideal for this purpose, although it was entirely unexpected that they would be capable of depositing metals and the other porous-structure materials defined within the depths of an essentially porous structure.